Method and apparatus for utilizing waste heat



June 21, 1932. c. LORENZEN METHOD AND APPARATUS FOR UTILIZING WASTEHEAT.

Filed Aug. 14, 1925. Sheets-Sheet 2 June "21, 1932. 1164;448

umuon AND APPARATUS FOR UTILIZING WASTE mm c. LORENZE'N Filed Aug. 14,1925 5 Sheets-Sheet 3 I llllllilll\tv\\u-\\:l llfllllllllll w S 2 My 05N. Tm m M; r VN T W e m K k 4 Penman -21, 1932 UNITED. STATES. PATIENTOFFICE v CHRISTIAN IDBENZEN, OI BERLIN, GERMANY, ASBIGNOB, BY IESNEASSIGNMENTS, TO

BENDIX AVIATION CORPORATION, 01' CHICAGO, ILLINOIS, A. CORPORATION OIDELAWARE METHOD AND arranarus roa uirmzzrue was'rn m'r' Applicationfiled August 14, 1925. Serial no. 50,274.

Whenfuel is burned for the generation of steam, considerable attentionis pald, as a rule, to an. economic consumption of fuel. In otherindustrial applications, however,

the utilization of the heat contents of the fuel is generally a verypoor one, and a large amount of heat is wasted. This is true, forinstance,-with respect to gas works, foundries, blast furnaces, furnacesfor melting or annealing. glass, for the manufacture of ceramic ware,etc.

The object of my present utilize waste heat available in plants orfurnaces of the character mentioned above, mak- 16 ing as few changes aspossible in the existing plants and their mode of operation.

In the examples illustrated by the accompanying drawings, my inventionutilizes certain features disclosed in my Patent No.

1,601,402, which matured from my co-pending application Serial No.536,562, filed in the United States Patent Oflice on February 14, 1922.'My present application also is in art a division or continuation of myco-pen ing application Serial No. 666,648, filed in the United StatesPatent Ofiice on October 4, 1923 which issued on February 19, 1929 .asUnited States Patent #1,702,264.

.Fig. 1 of the accompanying drawings is a diagrammatic elevation, withparts in section, showing a satisfactory way of applying my invention togas works; Fig. 2 -1s a cross section on line 22 of Fig. 1; Fig. 3 is asimilar view showinishow my invention may be used' in steel wor andparticularly in connection with a converter; Fi s. 4 and 5 show twoarrangements for utihzing the waste heat of combustion gases on theirway to a stack or other outlet.

In Figs. 1 and 2,- the brick structure or chamber 1 contains, in itsupper portion, the

retorts 2 in which illuminating gas is produced in the usual manner. T eretorts are heated by means of gases generated in thecombustion chamber'3 from fuel (coke) burning on thegrate 4. The chamber 3 is locatedbetween walls 5which together with wall portions 6 define anair chamber7 hav-.

ing an air supply connection 8 provided with a valve 9 for regulatingthe admission of air,

invention is to or shutting it off entirely when desired. The combustiongases from the chamber 3 pass first through a chamber 10 between theretorts 2, then over said retorts, and then down in the space or chamber11 located between the outer wall or brick structure 1 and the inner.wall portions '6. At the bottom, the space 11 is adapted to communicatewith a chamber 12, the connection between 11 and 12 being controlled bymeans of a sliding damper 13 or equivalent device operatable from theoutside, as indicated. The chamber 12 communicates with the stack orother outlet (not shown). Below the grate 4 I have indicated a pan 14adapted to contain water,

to moisten the primary air which is admitted below the grate through achannel 15 controlled by a valve or equivalent device 16.

in the chamber 3 is mixed with additional air and consumed to producethe proper heat in the chambers 10 and 11. Part of the heat is absorbedby the walls 5, 6 and transferred to the air flowing through the chamber7.

At 18 I have indicated a two-path heatexchanger or heat-transferrer ofan I suitable construction. One of the paths 0 this apparatus has aninlet connection 19 adapted to receive combustion gases from the lowerportion of the chamber 11, and an outlet connection 20 leading to thechamber 12.- Through an inlet connection 21, the other path of the heattransferrer receives com ressed air from the stationary collector or'fiusor 22 of a turbo-compressor, the rotor body of which, 23, hasinlets 24 through which air reaches the inner ends of the hollow blades25, which while rotating compress the air and project it into thecollector or difl'usor 22. After passing from the difiusor through theone path of the heat-transferrer 18, and absorbing heat fromthe hotcombustion gases flowing through the other path of said transferrer, thehot compressed air is led through terial to my present invention, andmay be of the character disclosed more fully in my Patent No. 1,601,402above referred to. The exhaust air from the turbine passes throughsuitable outlets 29 into a collecting channel 30 and a pipe 31 leadingto the air chamber 7. A branch pipe 32 may be provided for leading aportion of the warm exhaust air to a heat-economizer 33, here shown asan apparatus having two chambers or paths through one of which suchexhaust air flows to a-pipe 34'leading to the channel The other path orchamber of the economizer 33 is adapted to contain water, the steamgenerated therefrom being conducted to the place of use through a pipe-35. Of course, the heat of the air passing out through pipe 32 may beutilized in other ways than for the generation of steam. Another branchpipe 36 may connect the pipe 34 with the chamber 12, and I have alsoindicated a third branch pipe 37 connecting the pipe 31 with the channel15. Suitable valves 38, 39, 40, 41, and 42 control the pipe connections31, 32, 34, 36 and 37 respectivel At 43 I have indicated an electricstarter (motor-generator) of any approved construction, connected withthe turbine shaft 44, but any other suitable starting devicemay beemployed for starting the turbine.

At the beginning of the operation, the damper 13 is open, the valves 38,39, 40, 41, and 42 are closed, and the valves 9', 16 are open, theturbine being stationary. The retorts 2 are filled with coal, and cokeor other suitable fuel is placed on the grate 4 and ignited. Primarycombustion air enters through the valve 16 and channel 15, and passesupwardly through the grate. The generator gas produced by the combustionof the fuel in the chamber 3 passes upwardly and is mixed with airadmitted from the outside, through the valve 9 and air chamber 7, andissuing from the outlets 17 The combustion products pass through thechambers 10, 11, and 12 to the stack connection or other outlet. This issubstantially the usual way of operating the plant for the production ofilluminating gas by the distillation of the coal contained in theretorts 2. The gases escaping from the chamber 12 have a relatively hightemperature, say from 450 to 600 centigrade, and in the usual procedurethis heat is wasted. According to my invention, however, this heat isutilized, which is effected in the following manner with the apparatusshown in Figs. 1 and 2:

As soon as the operation has been started properly, the turbine is setin motion by means of the motor 43 or other suitable starting device.Then valve 38 is opened and damper 13 and valve 9 are closed. Thecombustion gases will pass from the chamber 11 through the pipe 19 andthe heat-receiving path of the heat-transferrer 18 to the outlet pipe 20and chamber 12, from which they escape to the stack or other outlet.While passing through'the heat-transferrer 18, the combustion gases giveup heat to the air which the action of the turbine blades forces throughthe other path of the transferrer. Such air enters at 24, passes throughthe hollow blades 25, thereby cooling them and itself becoming heated toa certain degree, as well as compressed by centrifu al action. Thecompressed air is received dry the collector or diffusor 22, from whichit passes through the pipe 21 to the heat-delivering path of thetransferrer 18 and thence through the pipe 26 to the distributingconduit 27 and turbine nozzles 28. The compressed air, highly heated inthe transferrer 18, and correspondingly expanded, strikes the outersurfaces of the rotor blades 25 and actuates the rotor. The exhaust air,still at a relatively high temperature. passes through the outlets 29,channel 30 and pipe 31 to the place where its heat is to be utilized.For instance, with the valve 38 open, such air will pass into thechamber 7 and issue from the outlets 17. By opening the valve 42, andproperly manipulating the valve 35, part or all of the exhaust air maybe directed through the pipe 37 into the channels 15, to pass upwardlythrough the grate 4. In practice, I do not consider it advisable to sendall the hot exhaust air from pipe 31 through pipe 37. Again, I may openthe valve 39, thus causing the hot exhaust air (or part of it, if thevalve 38 is open at the same sime) to pass through the heat-economizeror boiler I 33, the steam generated therein passing out through the pipe35 to a ,steam engine or other place of use, while the air, cooled byits passage through the economizer 33, but still fairly warm, isdelivered either to the channels 15 (if the valve 40 is open) or to theoutlet chamber 12 (if the valve 41 is open) or to both places (if bothvalves 40 and 41 are open). It will be understood that the flow of hotexhaust air to the chamber 7 channels 15, economizer 33 and outletchamber 12 can be controlled by the several valves referred to above,not only for shutting off one or the other of said parts entirely fromthe supply of such hot air, but also to vari-,

ably apportion the flow of air fromthe pipe;

31 to two or more of the said parts. Genera ally speaking. the valves 9or '16 respectively r v120. channels 15 respectively are receiving shotsexhaust air; however, it is possible toipsup- I a will be closed whenthe chamber 7 or-the ply at the same time to the chamber 8 orto thechannels 15, both hot'exhaust air and i also cooler air through thevalves 9 or 16 respectively, in proportions that may be regulated by asimple adjustment of the various valves. If desired, the valves 9, 16,39 and 41 alone may be opened and the valves 38, 40, and 42 closed, sothat the hot exhaust will be used exclusively for heating the boiler 33.The valves may also be manipulated in other ways to suit the userspurpose.

I desire to emphasize part1cularly the fact 6 that I prefer to give theparts such proportions that the pressure of the air is not increased bythe heating which such air undergoes in the heat-transferrer 18, buttheressure of the air, throughout its path, wi 1 be at its maximum inthe diffuser 22, that is to say, for instance, the cross section of thepassage 25 is less than that of the passage 28. In the form of myinvention illustrated by Fig. 3, the heat transferrer 18 and theconnection 26 leadin from its hot compressed air outlet to theistributing conduit 27 are practically the same as in Fig. 1, as arealso the parts 22, 23, 24, 25, 26, 28, 29, 30 and 43, the latter beingsecured to the turbine shaft 44' which, inthis case, in addition to theturbine rotor 23, carries the rotor 45 of a centrifugal air compressorthe stationary casing 46 of which receives warm compressed air from thedifi'user 22, through a pipe 47. This com pressor effects a furthercompression of the air, to a higher pressure, and the air thuscompressed in two successive stages passes from an annular collectorchannel 48 of the said.

compressor through a pipe 21' to the inlet of the heat-receivin g pathof the transferrer 18, the outlet of this path being connected with thepipe 26. The other or heat-delivering ath of the transferrer 18 has itsoutlet at 20 mto the atmosphere or to any other suitable place (whichmight be a boiler such as shown at 33 in Fig. 1), the inlet of saidsecond path being connected by a pipe 19' with the outlet 49 of aBessemer converter or like apparatus 50, the grate of which is indicatedat 51 while 52 designates an air chamber or blast chamber located underthe grate and receiving the hot air exhaust from the turbine, by way ofa pipe 31'. The trunnion axis about which the converter 50 swings, isindicated at 53. During the time that hot air is being blown through thecharge, the converter is in the position shown, with the outlet 49fitted in a substantially air-tight manner. against the inlet end of thepipe 19.

In this form of my invention as well, it is not intended that theheating which the compressed air undergoes in the transferrer 18 shouldraise the pressure of said air; in other words, at no point of its pathhas the air a higher pressure. than in the collector channel 48.

The element indicated" at 43 in Fig. 3 has been described as amotor-generator to. producecurrent while the turbine is delivering ower.Instead of this, the element 43 may e simply a dynamo to take anysurplus power delivered by the turbine, the main function of the turbinebeing the compression of the air which is delivered as a hot blastthrough the pipe 31.

In the construction illustrated by Fig. 4, the turbine rotor 23 mountedon the shaft. 44" has a chamber 54 extending from its central portion tothe interior channels of the blades 25, which through a stationary guidevane ring 55 of anywell-known or approved construction delivercompressed air into the annular collector or difiusor 22'; Thecompressed air then passes through the pipe 21" to one path of the heattransferrer 18', which path is formedv by a coil located in a stack 56constituting the other path of the heat transferrer in this form of myinvention. The compressed air thus heated by the waste heat which wouldotherwise escape unused, passes through the pipe 26' to the distributingconduit 27 provided with nozzles which discharge the driving mediumagainst the outer faces of the blades 25', such medium then, passingthrough a coil 57 located in a tank 58 containing a liquid (for instancefeed water) to be heated by the exhaust air. Through a pipe 59 theairthus cooled passes to a station ary annular channel 60 deliveringsuch air to the central portion of the chamber 54. It will be seen thatin this form of my invention the air circulates over and over againthrough the continuous closed path 54, 25', 55, 22', 21", 1s, 26, 27',30', 31', 57, 59, 60, 54.. In the heat transferrer 18, such air takes upwaste heat but its pressure is not increased thereb In this form of myinvention, the waste eat taken up by the compressed air in thetransferrer 18 is utilized partly in the turbine (the energy of the flowof said air being increased by such heating) and partly in the apparatus57, 58 which may be a feedwater heater.

Still another form of my invention is illustrated by Fig. 5. At 61 Ihave indicated afurnace provided with a grate 62 below which is locatedan air supply chamber 63. Air directly from the atmosphere or from theoutlet of a blower (not shown) may be ad-' mitted through a pipe 64controlled by a valve 65. The hot combustion gases, after passingthrough one path of a heat transferrer 18, reach the outlet 66. Thefurnace is used for heatinga boiler or other device (not shown) whichmay abstract heat from the dombustion gases before they reach thetransferrer 18, so that the latter utilizes the residual or waste heatof such gases. The other path of the heat transferrer has its mletconnected by a pipe 21, with the collector or diflusor 22, while fromthe outlet of said path a pipe 26 conveys the heated compressed air tothe distributing conduit 27 a from the nozzles 28 of which the drivingmedium is discharged against the outer surfaces of the turbine blades25. Cool air, drawn in through the stationary inlets 24 and through thechamber or channels 54 of the rotor body 23 mounted on the shaft 44,passes outward- 1y through the hollow blades 25, thus cooling thelatter, and is projected in a compressed or below it, or to both places,according to the position of the dampers 38 and 40 respectively. I

When starting the furnaceg the dampers 38, 40 are closed, and thevalveopened, the turbine being inactive. When combustion is under way, therotor of the turbine is started in any approved manner, the valve 65closed, and damper 40 opened, damper 38 being also opened if required tosecure better combustion. The turbine rotor will send compressed airthrough the heat transferrer 18, and the compressed air thus 'heatedwill operate the turbine, the hot exhaust air then passing to thefurnace to support combustion. Since such air is heated, combustion inthe furnace will become more active than during the admission ofrelatively cool air through the pipe 64. The temperature will thereforealso riseat the heat transferrer 18, and the compressed air passing tothe turbine through the pipe 26 will be hotter than before. Similarly,the temperature of the hot exhaust air will rise. Of course, thisincrease of temperature will not continue indefinitely, since a limitwill soon be attained at which the losses due to radiation will preventa further rise. g

The advantages of the invention are numerous and important. In thoseforms of my invention where the hot exhaust air is used to support orassist combustion, the forced draft thus obtained permits the stack orchimney to be reduced in height considerably, or dispensed withaltogether. In these cases, the fact that heated air is employed tosupport combustion, enables me to effect a material saving in fuel. Ineach of the constructions illustrated, the turbine will generallydevelop power in excess of that required for compressing and pro ellingthe air, and this excess energy may e utilized for driving variousmachines or appliances, or for producing electric current, as with theaid of a dynamo such as'indicated in Figs. 1 and 3. Of course, it is notnecessary that all of these advantages be present in every case, and therelative importance of the several advantages may vary according to thecon' ditions in individual cases.

Various modifications may be made without departing from the nature ofmy inventi on as set forth in the appended claims.

As has been explained above, the heating of the compressed air by thewaste heat is not intended to increase the pressure of said air, but ofcourse the resulting expansion of the air will increase the velocity ofits flow and thereby the kinetic energy which is available for theperformance of work.

It will also be noted that the hot exhaust fluid escaping from theturbine after performing wor therein, is subsequently sub- 'ected toconditions which successively alter its temperature, first in onedirection and then in the other; that is to say, the temperature isfirst increased (in those forms of my invention where the exhaust air isused for su orting combustion) or decreased (as in t e orm of myinvention illustrated by Fig. 4) and subsequently decreased (in theforms illustrated by Figs. 1,3 and 5) or increased (in the formillustrated by Fig. 4:).

The term industrial system from which waste heat is given off, as usedin the claims, is intended to signify any system in which heat is usedfor producing some particular fluids or other heat which is not utilizedin I performing the primary function of the apparatus and which is nolonger useful for that purpose, but which, on account of itstemperature, still contains suflicient energy to do some work of a typeindependentof the primary function of the apparatus.

I claim:

1. Method of treating a gas which consists in compressing the gas,transferring thereto waste heat, compressing and simultaneously heatingadditional gas by the energy of said heated gas, and thereafter usingsaid heated gas for heating.

2. Method of utilizing waste heat which comprises compressing a fluidand simultaneously heating said fluid by the fluid by which the fluid tobe heated is compressed, further heating said compressed fluid by saidWaste heat, using said heated, compressed fluid for heating andcompressing further fluid and for simultaneously doing other work, andusing the remaining heat in said heated and compressed fluid.

3. Method of utilizing waste heat which comprises compressing a fluidand simultaneously heating said fluid by the fluid by which the fluid tobe heated is compressed, further heating said compressed fluid by saidwaste heat, using said heated, compressed fluid for heating andcompressing further fluid and for simultaneously doing other work, andusing said heated and compressed fluid for aiding the combustion fromwhich said'waste heat issues.

4 Method of utilizing waste heat contained in combustion gases whichcomprises compressing a fluid and simultaneously heating said fluid bythe fluid by which it is com- 5 pressed, further heating said com ressedfluid by the waste heat of said com ustion gases, using said heated andcompressed fluid for heating and compressing other fluid and for doingother work, and thereafter using said heated and compressed fluid foraiding the combustion which produces said gases.

5. An industrial system from which waste heat is given ofl, and meansfor utilizing said waste heat comprising a two path heat exchanger, onepath of said heat exchanger being adapted to receive said waste heatfrom said industrial system, a fluid compressor, the other path of saidheat exchanger being connected to the outlet of said compressor, saidcompressor being driven by the gases from said second path, and aconnection from said second path whereby fluid used in driving saidcompressor passes-to the industrial systom to aid combustion therein.

6. An industrial system from which waste heat is given off, and meansfor utilizing said waste heat comprisin a fluid compressor, means forheating the fluid emitted from said compressor by said waste heat, meansfor driving said compressor byvsaid heated fluid, and means for usingsaid fluid in said system.

7. An industrial system from which waste heat is given off, and meansfor utilizing said waste heat comprising a fluid compressor,

means for heating the fluid emitted from said compressor by said wasteheat, means for driving said compressor by said heated fluid, and meansfor using said fluid to aid combustion in said-system.

40 8. An' industrial plant from which waste heat is given off in theexhaust gases of combustion, and means for utilizing said waste heatcomprising a two path heat exchanger, said exhaust gases flowing throughone path of said heat exchanger, a fluid compressor,- the fluid acted onby said compressor passing through the second path of said heatexchanger, said heated and compressed fluid being adapted to operatesaid compressor and simultaneously to heat the fluid being compressed,and means for thereafter using said heated and compressed fluid foraiding in the combustion in said system.

In testimony whereof I have hereunto set my hand.

' CHRISTIAN LORENZEN.

